The present invention has for its object a socket member for electrical connectors of the pin and socket type, and the method for making same.
More particularly the socket member object of the present invention is of the type in which its inner areas which establish the contact with the pin member are, when the said pin member is not inserted, arranged at least approximately according to a family of straight generatrices of a hyperboloid of one sheet. In this manner, upon insertion of the pin member into the socket member, the said inner contact areas of the socket come to elastically bear against the surface of the pin member, thus ensuring an efficient electrical contact between the said two members of the connector.
A socket member of this type is known, for example, from the Italian Pat. No. 604 272 (Bonhomme) according to which the socket presents at its interior a plurality of contact wires, arranged according to straight generatrices of a hyperoboloyd. The contact wires are secured at the interior of the socket so as to be tensioned between a pair of coaxial circumferences and are blocked onto a cylindrical sleeve, which constitutes the body of the socket, by means of two locking rings force-fitted onto the extremities of said sleeve. The socket according to the mentioned Italian Pat. No. 604 272, although it presents excellent features of electrical contact between the socket and the pin, is rather complex in its construction and consequently requires for its making particular methods and devices, and this obviously leads to a high cost of the final product.
According to U.S. Pat. No. 2,450,529 (Sprigg) a socket member is obtained by cutting opposite sides of a cylindrical sleeve to form two slots extending in planes diagonally disposed with respect to each other, and by reducing the diameter of the sleeve bore by turning one end of the slotted socket with respect to the other end. However the slots are cut so as to present parallel flanks or sides, which leads to irregularities in the deformation upon twisting of the slotted socket, particularly in the areas of contact between socket and pin, with consequent difficulty of insertion, jamming and deterioration of the pin member, and malfunctioning of the connector.
The socket member according to the present invention is obtained thanks to permanent deformation by twisting of a cylindrical sleeve of suitable metal, provided with through slots arranged on its cylindrical surface and inclined with respect to the longitudinal axis of the sleeve. The characterizing feature resides in the fact each slot, previously to its twisting deformation, presents a transverse profile with sides diverging towards the exterior, and some sides meet at the ends of the slot forming curvilinear edges in such a manner that the vertices of said edges located on the inner surface of the sleeve are nearer to each other with respect to the vertices of the edges located on the outer surface, which are farther from each other. The said particular shape of the slots contributes in a determining manner to the correct deformation upon twisting of the sleeve, so that the strips defined by the slots tend to be arranged according to a family of straight generatrices of a hyperboloid of one sheet, taking in consideration the composite stresses of traction-compression and torsion which take place precisely upon twisting of the sleeve. In this manner there is avoided the formation of irregularities, such as sharp edges or warped surfaces, in the areas of contact at the interior of the thus formed socket.
According to another characteristic feature of the invention, it has been found that an angle of inclination of the slots between 5.degree. and 20.degree. (and preferably between 8.degree. and 10.degree.) is particularly advantageous.
Still according to another feature of the invention, it has been found that, by selectively reducing the thickness of the cylindrical wall of the sleeve at one zone, it is possible to select the positioning of the zone of maximum reduction of the diameter of the sleeve (upon twisting) and consequently the positioning of the areas of contact for the pin member.
The invention also relates to a method for the making of a socket member for electrical connectors of the above mentioned type, comprising the following basic steps:
obtaining a cylindrical sleeve of any suitable metal, presenting an inner axial bore having a diameter which is equal or smaller than the final diameter; PA1 cutting, by means of a double-angle milling cutter, of through slots arranged along the cylindrical surface of the sleeve and inclined with respect to the longitudinal axis of the sleeve; PA1 finish boring and grinding of the inner surface up to the required final diameter, if necessary; PA1 twisting of the slotted sleeve of a predetermined angle, in the same direction as the inclination of the slots.